I have a Lonestar Special and absolutely love it. However, I've had a recurring problem.

Every now and again the sound fizzles out (completely out), and comes in and out at random. I've isolated the issue to be within the effects loop. If I hit bypass switch the problem is gone.

It went back to the store and they were advised by their Mesa distributer that it was just the pre-amp valve in the effects loop. They switched it out, it's been fine for a few weeks and now it's happened again. It's already been back to the store on two occasions and is likely to be going back again.

I only use the effects loop to have use of the master/solo boost volume controls so I can get by without it. I just shouldn't have to.